1. Field of the Invention
The present invention relates to a magnetic sensor utilizing the rotation of spins by external magnetic fields, particularly to a spin transport type magnetic sensor.
2. Related Background Art
Magnetic heads of hard disk drives (HDDs) are magnetic sensors utilizing magnetoresistance effects. Tunnel magnetoresistance (TMR) devices used for magnetic heads have a spin-valve structure and have a superior property that it can provide relatively significant change in output. However, it is believed that, when an improvement in magnetic data readout speed is required, especially readout of magnetic data having a record density of 1 Tbit/inch or more is required, a different detection principle of magnetic heads needs to be applied in order to detect the magnetic data.
In order to address such problem, the present applicant have proposed a spin transport type magnetic sensor utilizing a spin current flowing through a semiconductor layer in a SOI (Silicon on Insulator) substrate (see Japanese Patent Application Laid-Open. No. 2011-176012). Generally, Si has a spin diffusion length of 1 μm or less and a spin lifetime of 1 nsec or less.
However, there is still a room for improvement in spin transport properties of spin transport type magnetic sensors using SOI substrates. With the foregoing in view, it is an object of the present mode to provide a spin transport type magnetic sensor which can improve spin transport properties.